org.sonar.process.ProcessCommands.java Source code

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Here is the source code for org.sonar.process.ProcessCommands.java

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/*
 * SonarQube, open source software quality management tool.
 * Copyright (C) 2008-2014 SonarSource
 * mailto:contact AT sonarsource DOT com
 *
 * SonarQube is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * SonarQube is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.process;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

/**
 * Process inter-communication to :
 * <ul>
 *   <li>share status of child process</li>
 *   <li>stop child process</li>
 * </ul>
 *
 * <p/>
 * It relies on files shared by both processes. Following alternatives were considered but not selected :
 * <ul>
 *   <li>JMX beans over RMI: network issues (mostly because of Java reverse-DNS) + requires to configure and open a new port</li>
 *   <li>simple socket protocol: same drawbacks are RMI connection</li>
 *   <li>java.lang.Process#destroy(): shutdown hooks are not executed on some OS (mostly MSWindows)</li>
 *   <li>execute OS-specific commands (for instance kill on *nix): OS-specific, so hell to support. Moreover how to get identify a process ?</li>
 * </ul>
 */
public class ProcessCommands {

    private final File readyFile, stopFile;

    public ProcessCommands(File directory, String processKey) {
        if (!directory.isDirectory() || !directory.exists()) {
            throw new IllegalArgumentException("Not a valid directory: " + directory);
        }
        this.readyFile = new File(directory, processKey + ".ready");
        this.stopFile = new File(directory, processKey + ".stop");
    }

    // visible for tests
    ProcessCommands(File readyFile, File stopFile) {
        this.readyFile = readyFile;
        this.stopFile = stopFile;
    }

    public void prepare() {
        deleteFile(readyFile);
        deleteFile(stopFile);
    }

    public void endWatch() {
        // do not fail if files can't be deleted
        FileUtils.deleteQuietly(readyFile);
        FileUtils.deleteQuietly(stopFile);
    }

    public boolean isReady() {
        return readyFile.exists();
    }

    /**
     * To be executed by child process to declare that it's ready
     */
    public void setReady() {
        createFile(readyFile);
    }

    /**
     * To be executed by monitor process to ask for child process termination
     */
    public void askForStop() {
        createFile(stopFile);
    }

    public boolean askedForStop() {
        return stopFile.exists();
    }

    File getReadyFile() {
        return readyFile;
    }

    File getStopFile() {
        return stopFile;
    }

    private void createFile(File file) {
        try {
            FileUtils.touch(file);
        } catch (IOException e) {
            throw new IllegalStateException(String.format("Fail to create file %s", file), e);
        }
    }

    private void deleteFile(File file) {
        if (file.exists() && !file.delete()) {
            throw new MessageException(
                    String.format("Fail to delete file %s. Please check that no SonarQube process is alive", file));
        }
    }
}